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AVIAN BOTULISM IN SAMBHAR LAKE

Written by Talent KAS

Related Topic in KAS Prelims Syllabus:

Science and Technology [Paper-II]: Public Health and Community Medicine, Health Care.

News

Indian Veterinary Research Institute (IVRI), Bareilly has confirmed avian botulism as the reason for mass mortality of birds, including migratory species from Northern Asia, at Sambhar Lake in Rajasthan.

What is Botulism?

  • It is a serious neuro-muscular illness caused by a toxin produced by the bacterium Clostridium botulinum.
  • Clostridium botulinum produces dangerous toxins (botulinum toxins) under low-oxygen conditions.
  • It is commonly found in the soil, river, and sea water.
  • There are around eight types — A, B, C1, C2, D, E, F, and G — of botulinum toxin.
  • Botulinum toxins are one of the most lethal substances known.
  • Botulinum toxins block nerve functions and can lead to respiratory and muscular paralysis.

Avian botulism

  • Botulinum affects both humans and animals but the type of the toxin varies — botulinum C in birds and A, B and E in humans.
  • It affects the nervous system of birds, leading to flaccid paralysis in their legs and wings and neck touching the ground.
  • The toxin has been recognised as a major cause of mortality in wild birds since the 1900s.

What happened at Sambhar?

  • According to the report by IVRI, avian botulism that caused the mass die-off at Sambhar was caused by the climate.
  • Water levels were fluctuating throughout the year. Due to a good monsoon this year, the water level reached the lake bed after a gap of 20 years.
  • Good monsoon provided a favourable environment for the bacteria to spread. The bacteria needs anaerobic (absence of oxygen) conditions and does not grow in acidic conditions.
  • The monsoon brought a large population of crustaceans (like shrimps, crabs, and prawns), invertebrates (snails) and plankton (like algae) with it.
  • These living organisms are capable of hosting the bacteria for a long period of time.
  • According to another theory, ‘a bird-to-bird cycle’ could also have led to the tragedy.
  • In such an event, maggots feeding on dead birds can concentrate the toxin. Birds feeding on dead birds can get affected.
  • This was observed in Sambhar too as researchers found only insectivorous and omnivorous birds affected and not herbivores
  • IVRI report discounted external factors like water pollution and eutrophication as no farming was being carried out in the vicinity and the runoff from the same was not possible.

Way Forward

  • State Government should pass legislation in the Assembly to create a Sambhar Lake Development and Conservation Authority.
  • This authority should be handed A to Z responsibility of Sambhar Lake.
  • Clostridium botulinum needs protein to produce botulism toxin. Since animal carcasses are an excellent source of protein, removing them reduces the resources the bacterium needs to produce toxin and can help reduce or eliminate toxin production.
  • Botulism outbreaks are likely to become more frequent as climate change alters wetland conditions to favour bacteria and pathogens.
  • In addition to the efforts for mitigating climate change, establishment of rescue and medical centres is also the need of the hour.

[Source: Down To Earth, The Hindu, Indian Express]

 

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